The Effect of the Additives in the Polymerization Medium on the Gas Permeation Behavior of Polyamide Thin Film Composite Membranes Prepared by Interfacial Polymerization

In this research, the effects of the presence of additives such as sodium dodecyl sulfate (as a surfactant) and sodium carbonate (as acid acceptor) on the top layer characteristics and gas separation properties of composite membranes, prepared by an interfacial polymerization method, were studied ATR-FTIR and SEM techniques showed the important role of the additives on the structural density and thickness of the top layer. As a result, the top layer of the prepared sample in the presence of both additives was the densest and the thickest while that of the sample prepared in the absence of both additives was the thinnest one. Furthermore, based on the AFM results, the composite membrane prepared in the presence of just sodium carbonate presented the roughest (Rmax = 520 nm) and that prepared in the presence of both additives shows the smoothest (Rmax = 148 nm) surface. Investigation of the gas permeances of membranes shows that the membrane with top layer prepared in the presence of just sodium carbonate has the highest CO2 permeance (25.2 GPU), due to its thin and rough top layer. Moreover, the highest CO2/CH4 selectivity (58) was obtained by the composite membrane prepared in the presence of both additives. On the other hand, the highest CO2/N2 and CO2/O2 selectivities (63 and 54, respectively) were achieved through the utilization of the composite membrane prepared in the presence of just sodium dodecyl sulfate.